1. Field of the Invention
The present invention relates to a standing wave barrier for a radio frequency cable having a cable axis, in particular a coaxial cable, of the type having at least one metallic base web that proceeds parallel to the cable axis from a first web end to a second web end, the web ends are coupled with one another in terms of radio frequency via a capacitance, so that the base web and the capacitance together form a radio frequency resonant oscillator circuit.
2. Description of the Prior Art
Such standing wave barriers are generally known. They are used in particular in magnetic resonance installations in order to damp radio frequency disturbances (interference) in the outer shielding of coaxial cables that proceed from local coils to an evaluation device of the magnetic resonance installation.
In the prior art, it is known to wind the cable to resemble a coil having a number of windings, and to connect the ends of this coil with a capacitor in terms of radio frequency. In addition, in the prior art it is known to solder a wave trap onto the external conductor,(shielding) of the coaxial cable, and to electrically connect it at its end to the external conductor via a capacitor (e.g., again via a solder connection).
In both of these known arrangements, the cable in which the standing wave is to be damped is a component of the standing wave barrier. The standing wave barrier therefore can be completed and tuned only after being connected to the cable.
From German OS 102 11 635, a standing wave barrier is known for a radio frequency cable having a cable axis that has a hollow cylindrical Inner structure. The inner structure is electrically conductive, e.g. metallic, and proceeds parallel to the cable axis from one axial end to the other axial end of the standing wave barrier. The standing wave barrier surrounds a segment of the radio frequency cable and is capable of being displaced along the radio frequency cable. The axial ends of the standing wave barrier are coupled with one another in terms of radio frequency via a capacitance, so that the internal structure and the capacitance unit together form a radio frequency resonant oscillator circuit.
From German PC 196 27 027, a standing wave barrier for a radio frequency cable having a cable axis is likewise known. This standing wave barrier is inductively coupled to the radio frequency cable. For this purpose, it has a metallic web that proceeds parallel to the cable axis from one axial end of the web to the other axial end of the web. The web ends are coupled with one another in terms of radio frequency via a capacitance, so that the inner structure and the capacitance together form a radio frequency resonant oscillator circuit. The standing wave barrier of German PS 196 27 027 also can be displaced along the radio frequency cable.
From German Utility Model-83 18 583, a cylindrical coupling element is known that has a terminal that can be coupled inductively to the inner conductor of a coaxial cable via tile outer shielding of the coaxial cable. The coupling element is composed of two half-shells that can be connected to one another such that the radio frequency cable is clamped between them. As a result of this design, the coupling element is situated on the coaxial cable so as not to be capable of being displaced.